The present invention relates to a novel inorganic filler and to a thermoplastic resin composition filled with same. More particularly, the present invention relates to an inorganic filler comprising a powdery inorganic compound coated with a fatty acid ester of a polyhydric alcohol as well as a synthetic thermoplastic composition comprising same.
From the past, a variety of powdery inorganic compounds are known as inorganic fillers for synthetic resins. As powdery inorganic compounds are generally hydrophilic at the surface thereof, they have poor affinity to hydrophobic or oleophilic synthetic resins and so cannot be incorporated in a large amount into such resins to significantly modify the physical properties of moldings obtained therefrom. As a method widely adopted hitherto for overcoming this drawback, such powdery inorganic compound is coated with a fatty acid or a metal salt thereof before actual use.
Since these known conventional coating agents have a low softening or melting point, they have such a shortcoming that they undergo pyrolysis and seriously reduce their covering characteristics when exposed under high temperatures.
As a result of extensive researches made for developing an inorganic filler of good quality which is devoid of such drawbacks and can be incorporated in a large amount into resins, it has now been found that the various problems can be solved by using as a filler a powdery or powdered inorganic compound coated with a fatty acid ester of a polyhydric alcohol and that the use of such inorganic filler serves to improve flowing characteristics and is especially effective for improving kneadability with resins so that various physical properties such as impact-strength of the resulting moldings can remarkably be improved and enhanced. The present invention has been accomplished on the basis of the above finding.